Results of traditional staging techniques will be considered as the "gold standard" tests for mediastinal diagnosis and staging. These tests will be used as the standard to which other modalities and combinations of modalities are compared. Data will be collected and analyzed as a whole (all patients with mediastinal LN sampling) and separately based on pre-biopsy diagnosis, post-biopsy diagnosis, mediastinal LN size (CT scan), LN station and PET avidity. Sensitivity, specificity, positive and negative predictive values, likelihood ratios and accuracies will be calculated and used to compare EUS and EBUS (transluminal strategy) to traditional staging, EUS to EBUS, EUS to traditional staging and EBUS to traditional staging. Subanalysis based on pre-biopsy patient and imaging (CT and PET) characteristics as well as ultrasound imaging characteristics during biopsy will be used to develop predictive models for minimally invasive mediastinal diagnosis, in order to better define patients at increased or decreased likelihood of successful diagnosis using these techniques. ROC curves will be constructed and used to discriminate results between diagnostic tests.